Bridging...

[parabolic 0]

So has the bridging gotten any better in Cura in the latest builds? I cant seem to find any way to adjust the speed and flow for just bridging. Im printing a standard bottle opener right now and it doesnt seem to change its speed or direction for bridging...Id like to be able to tweak that as my prints are great but certain bridges seem to droop and not fully connect. Id like to be able to slow it down for that operation.

Thanks

 

[pm_dude 27]

I have not seen anything for this but I would be interested in learning too

My guess is that if it ever get to exist it will be able to change the speed and maybe the flow but not the nozzle temp because it takes too much time to change for such small section.

[gr5 2,167]

I really wish Cura would put a comment in the code for when a bridge starts and ends. Then you could potentially increase flow a bit or at least slow down acceleration a lot (maybe 1000mm/sec/sec) with a plugin.

 

[Daid 306]

There have been some changes, moving bridges from "per layer" to "per area". Properly detecting a bridge still fails on some cases. There is a github issue which has some ideas on how to improve it.

The problem with the "add comment" or "change speed/flow" is that when I get to the part of exporting the GCode, I no longer have the information associated with if it's a bridge or not. All the infill lines (bridges/tops/bottoms/sparse) are thrown on a single pool to be printed.

 

[parabolic 0]

hmm.... so is there going to me options in the Expert settings for instance to have control over bridging then? Im kinda lost on what was stated above...

 

[Daid 306]

hmm.... so is there going to me options in the Expert settings for instance to have control over bridging then? Im kinda lost on what was stated above...

 

Not anytime soon.

 

[drofnas 15]

What's the recommended process/application if you print has any sort of bridging?

I just got my printer today and seem to be having issues with any prints that have a bridge in them.

Basically my process is:

 

1. Download stl's from multiverse (Thingiverse / YouMagine)
   
2. Open in Cura
   
3. Position things™
   
4. Save gcode to SD Card
   
5. Stick in printer
   
6. Print.
   

I have a UM2 and using the Ultimaker Blue that came with my printer. Only calibration I've even done was the initial bed leveling.

Bad Bridge: (don't have gallery upload permissions, yet)

https://www.dropbox.com/s/cldymxdxo3plv15/2014-08-14%2021.43.23.jpg

 

[pm_dude 27]

Overhang are always difficult without support. Try adding supports (but quality will not be perfect) and try printing slow 20-30mm/s , cold (200-210C) and with 100% fans.

Default fan settings will progressively get the fan at 100% only at 5mm height. Try changing that to 0.5mm instead (in the expert settings)

[jameshs 42]

You would be amazed what can be printed as a bridge without support - but it depends heavily on temp, speed fan direction and the filament.

I have been printing the fairphone cases that have two large (15mm and 20mm) bridges and with some filaments at 215 and 30mm/s they print beautifully - with others they string on the first two or three and then print beautifully (and trimming off those two is absolutely undetectable on the finished product.

Watching a 20mm bridge happening in a single wall product is like watching a spider weave a web - mesmerizing.

However, it is tricky as you want sufficient temp to bond the layers (a single shell, 1mm gap, single shell) as insufficient bond and the phone case just snaps.

so mess about with your printing temps to see what works for bridging best.

You can't just download stuff and press print - you have to evaluate every model with a skilled eye to see if the originator thought about printing and I have to say that often on thingiverse they did not!

Prioritize ones where there is actually a print there - and the instructions tell you the ideal settings. In skilled hands these machines are amazing!

James

 

[drofnas 15]

It might be a while before I have any sort of "skilled hands" (eyes) :-)

I wish there was a database of knowledge for material X trying to print a model with A, B, C features on it. For example, being able to search for Colorfabb XT and trying to print a Model that has a 20mm overhang. If said search doesn't come up with anything, it would give them the option to toss their findings up. Hmm, maybe if I have time I'll toss something like this together, at the very least to track my own tests/settings.

But anyways, I'll try messing around with the temp, speed, and I always keep the fans at 100% (not sure if I should ever change that). The print I was trying to make with the overhang was a calibration piece (http://www.thingiverse.com/thing:24238). Even the small (5mm) overhang looked horrid; the overhand in my previous picture was the 10mm one.

Thanks for all the help.

 

[drofnas 15]

While playing around in the advanced/expert settings of Cura some more this weekend, I noticed the "Tweak at Z 3.2.1" plugin that was installed. This seems to be a good way to tweak your settings a few layers before the bridge happens, so that you can change the temperature of the hot-end and the flow rate of your filament.

I still haven't found the "perfect" settings for the "Ultimate Blue" filament yet. I start printing with 40mm @ 217c, then I reduce the speed to about 50% and the extruder to 200c a few layers before the bridge. I wanted to give it time to cooldown the extruder before the bridge, so I started this process about 5 layers before the bridge came up (this will depend on the side of your model). Then about 5-10 layers after the bridge I would increase the speed to about 75% and 210c, 5 layers after that I went back to 100% at 217c.

I did the 75% speed increment, since I wasn't sure if I could jump straight from 50% to 100% due to the extruder most likely not heating up quick enough. Might need even more increments, maybe increase the speed/temp by 10% until you reach full speed/temp.

It would be awesome if there was a plugin that automatically setup all of these steps for you. So you could say what layer the bridge starts at, how many layers before and after the bridge you want to ramp down/up, and the final ramp down temperature/speed. Then it would calculate all the increments it needs to jump down/up so the speed/temp stay in sync. Then if your printer needs smaller increments, you would simply increase the number of layers before/after the bridge to get the right values.

/2 cents from a newb 3d printer owner

 

[gr5 2,167]

I have found that bridges are pretty damn easy to print. Anyway here is some testing and results and conclusions I found (post #17):

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=25304

This was for PLA and if the filament has a different glass temperature than PLA (which is around 50-60C) then it will have very different bridging properties also. I have never used XT.

@drofnas - Did cura recognize bridging? If it doesn't recognize it then it will do diagonal lines across the bridge (bad) but if it *does* recognize that there is a bridge there then it does lines straight across the gap.

 

[zumfab 3]

I seem to have some trouble bridging. The first few layers are simply empty, the printer typically builds a little more of the bridge with every pass. This is much different than what I understand from others should happen, in that the printer should be laying a full string the first pass. Right?

Even in a short span (5 mm) there seems to be little proper bridging going on. I am not sure how to fix this. When I look at

I feel they are nothing like what I am seeing. Come to think of it, that is probably why I have had some trouble printing proper top surfaces when the shell is too thin.

 

[gr5 2,167]

. When I look at clips like this I feel they are nothing like what I am seeing

 

What's different? You didn't answer my question about diagonal versus straight. Look at it in layer view in Cura - is it straight like in the video or diagonal? If diagonal then something about the model fools Cura into thinking it is just an ordinary tilted overhang at 89 degrees instead of 90 degrees. Or something else about it is confusing Cura.

 

[gr5 2,167]

Oh. You didn't answer my question because I asked it of the other guy. Still... both of you now need to answer the question.

 

[drofnas 15]

Yea, it was doing straight lines for the first layer of the bridge, then did the diagonal lines over top the straight lines.

So, looking at your tests, it seems that 180c @ 50mm is the best setting to work with for bridging. This was the last 100mm bridge I tried before moving on to finally printing my "printer upgrades" :-)

https://www.dropbox.com/s/v0k6qfj8mtrt7ss/2014-08-18%2010.48.14.jpg

I'll have to try your settings when I get a chance tonight, see if those work for the 100mm bridge test.

 

@drofnas - Did cura recognize bridging? If it doesn't recognize it then it will do diagonal lines across the bridge (bad) but if it *does* recognize that there is a bridge there then it does lines straight across the gap.

 

[zumfab 3]

Oh. You didn't answer my question because I asked it of the other guy. Still... both of you now need to answer the question.

 

I seem to be missing your post with the question, but I think I get the idea: in layer view the layers seem straight. I am printing a 1x1x1 cm version of this cube - although the picture is made by someone else. I did not print this cube.

I tried setting the temperature from 210 to 217 like in the clip, but the result was less than spectacular. The surface quality was actually a lot worse and the intended bridging was slightly messier. There also was some unwanted bridging between the upright legs. I tried 190 and 200 degrees celcius before too, but former caused adhesion issues and the latter had trouble forming solid layers without separation between lines in the same layer, both an indication of the temperature being too low.

Maybe I need to try a modern dual fan design.

 

[gr5 2,167]

There also was some unwanted bridging between the upright legs

 

Completely different issue. Unrelated. We call that "stringing". There are many fixes for stringing. The most important is retraction. Test that Cura is actually retracting where you see stringing. To do that look at it in layer view. The blue lines are "non extruding moves". If the blue line has a vertical blue line sticking up at the start of the move - that indicates not head movement but retraction. Make sure you have that.

If you *do* have retraction and are still seeing stringing then you need to adjust your retraction distance or nozzle temperature. For UM Original print this clip to keep the bowden from moving on the print head and then after you do that 4.5mm retraction is usually the ideal retraction distance:

http://www.thingiverse.com/thing:46157

 

Also lowering nozzle temp helps reduce stringing - makes the PLA more like toothpaste instead of like honey. Of course you will also have to print slower if you print cooler - see first photo here:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

 

[zumfab 3]

Completely different issue. Unrelated. We call that "stringing". There are many fixes for stringing. The most important is retraction. Test that Cura is actually retracting where you see stringing. To do that look at it in layer view. The blue lines are "non extruding moves". If the blue line has a vertical blue line sticking up at the start of the move - that indicates not head movement but retraction. Make sure you have that.

 

I hear the telltale click clack during printing, but I double checked to be sure. Retraction is on and happening with standard and recommended settings.

 

Also lowering nozzle temp helps reduce stringing - makes the PLA more like toothpaste instead of like honey. Of course you will also have to print slower if you print cooler - see first photo here:

 

It was an experiment with a slightly higher temperature to see what the influence would be on bridging, but bridging, stringing and surface print quality all suffered. Lowering the temperature back to the old settings fixes all of that.

I will have a go at the clip you posted.

 

[pm_dude 27]

I did a print today with Colorfabb XT and the bridge (capping a 10mm wide cylinder) is just perfect. First layer was all good. Second layer covered it completely as if it wasnt even there. I cant say the same for FlexPLa but I'll find the good settings and I'm sure they will become as good